Anything from .25-'06 on up to .300 Win Mag--and a whole bunch of practicing. Memorize trajectory. Become really, really good at doping the wind.
Example: Back 40, maybe 45 years ago, I was quite competent for killing Bambi within around 300 yards. So one day I saw a nice buck, but it was a way-over-yonder shot.
I guesstimated 400 yards, and allowed for the wind by holding about on his nose for a drift to the heart. Held two feet above his heart area (zeroed for 200).
Heh. Bangity, bangity, no joy. Finally, he lifted a hind foot and sniffed.
Probably 550 yards, and more wind than I'd thought.
I stopped my foolishness. Unfortunately for him, he came down the hillside toward me. The wind dropped off. He stopped, facing me, and posed quite prettily. I held on top of his antlers; hit him low in the chest. Bang, whop, plop at about 450. Tasted good...
Real easy to feel plumb stoopid, though.